Long-wavelength topographic evolution in the pericratonic Argentine Pampas foreland: Interplay between lithospheric thickness and dynamic topography

Abstract

The Argentine pericratonic foreland, ∼900 km east of the trench, hosts a sedimentary basin recording repeated subsidence and uplift since the Paleozoic, commonly attributed to thermal evolution or mantle-driven dynamic topography, though their magnitude and persistence remain uncertain. We investigate the Cretaceous–Neogene evolution of the Pampas using one-dimensional backstripping from thirteen deep wells combined with pure-shear lithospheric stretching models. Residual topography was estimated by contrasting tectonic subsidence obtained from backstripping and stretching models, evaluated across minimum and maximum subsidence parameter bounds, and subsequently compared with recent global dynamic topography models. Early Cretaceous (145–100 Ma) subsidence is focused in synrift depocenters, consistent with stretching-dominated processes, but including the Paraná plume stage (130–100 Ma) reveals slight residual uplift. During the postrift stage (100–34 Ma), residual signals are low-amplitude, diffuse, and method-dependent, reflecting waning thermal subsidence and weak mantle forces. After ∼34 Ma, during Andean stages, residuals become spatially coherent, showing a southeastward-increasing subsidence pattern, reaching ∼150 m in the Neogene due to strong subcrustal influence. Comparisons with global dynamic topography models show only partial temporal agreement, indicating that long-term (during Early Cretaceous), large-scale subsidence patterns are primarily governed by lithospheric architecture rather than mantle flow alone. Long-wavelength vertical motions in the pericratonic foreland were thus mainly controlled by sedimentary loading and lithospheric thickening since Late Cretaceous-Early Paleogene, with dynamic topography acting as a secondary, transient overprint since the Oligocene. While lithospheric thickening would predict southward subsidence, a modern north-south transect reveals an increase in observed elevations. Such a mismatch indicates that transient and shorter-term (during the latest Andean stages) dynamic forces overprint the long-term lithospheric control, thereby reflecting the non-steady state nature of mantle-lithosphere interactions in the Argentine foreland.